The 777 will be a far more comfortable aircraft if DL is putting 9 across in the 787 coach section like most airlines are:
http://blogs.usatoday.com/sky/2006/0..._crammi_1.html
The 777 is 15-16 inches wider inside than the 787, so the 787 will be a tight squeeze, unless DL goes with 10 across in any new 777s like Air France and KLM are doing.